There is a variety of circuit applications in the automotive or industrial area where it is desired to drive an electrical load. In particular, there are applications in which it is desirable to limit a slew rate of a voltage across the load to a predefined maximum slew rate. Limiting the slew rate may help to reduce or prevent voltage peaks of voltages across parasitic inductances, and, therefore, may help to reduce EMI (Electromagnetic Interference).
Conventional drive circuits for driving electrical loads include an electronic switch, such as a power MOS transistor, connected in series with the load. The series circuit with the load and the electronic switch is connected between voltage supply terminals. Dependent on the desired operation state of the load, the electronic switch is either switched on in order to connect the load to the supply terminals, or is switched off. In these drive circuits, the slew rate of the voltage across the load is dependent on how fast the electronic switch switches from an off-state to an on-state and switches from an on-state to an off-state.
Power MOS transistors are voltage controlled devices that receive a drive voltage at a drive terminal (gate terminal) and that switch on and switch off dependent on the drive voltage. The switching behavior of the MOS transistor may be controlled by providing a filter coupled to the drive terminal and operable to filter the drive voltage. These filters, however, often require the use of passive components, such as resistors or capacitors. Such passive components are difficult to integrate in the semiconductor chip of the power MOS transistor. When implemented as discrete components on a PCB (Printed Circuit Board) such passive components increase the manufacturing costs of the drive circuit.
There is therefore a need to improve conventional drive methods and drive circuits.